Described in detail here.

Disasters are NOT an economic stimulus just because you see a lot of construction taking place afterwards. You're seeing mostly the work needed just to get back to square one, and it's absorbing resources that could otherwise have been used for real growth. 9/11 and Katrina were a blow to economic growth, no matter how you work it.

Highways--and almost all infrastructure come to that--are mostly funded at the state and local level (Federal funds make up about a quarter of the total for highways). Take up the potholes, cracked sidewalks, and busted water pipes with them. I've also done a lot of travelling, mostly in the West, and sometimes the difference in road quality is night and day across a state border. The bridge in Minneapolis fell down not because of a lack of infrastructure funding, but because the design stunk.

As for the 90s economy vs. the past four years, I've already challenged someone to pull up hard numbers on this. They exploded. Maybe you can do better. Be sure to check on the income gaps during the 90s, too.